> [...] but that seems like that would be a nightmare to keep two lists in sync since that file isn't in our directory.

Agreed, this would be really bad.

For this PR, I just tried implementing https://github.com/mozilla/pdf.js/issues/4005#issuecomment-30166296. As I stated, this PR is an attempt to address the concerns that was raised over the initial implementation, I don't expect that this is perfect as is.